The identification and production of volatile organic compounds (VOCs) continues to be a driving force in the development and expansion of many commercial industries. For example, 1,8-cineole, commonly referred to as eucalyptol, is the pharmaceutically active component of eucalyptus oil, comprising 70-85% of the essential oil. Traditional uses of eucalyptus oil primarily involve non-prescription pharmaceuticals, fragrances and degreasing detergents (Opdyke, 1975, Food and Cosmetics Toxicology 13: 91-112; Hong and Shellock, 1991, American Journal of Physical Medicine and Rehabilitation 70:29-33; Leung, Y. (1980). Eucalyptus. New York: Wiley; Furia, T., & Bellanca, N. (1971). Fenaroli's Handbook of Flavor Ingredients. Cleveland, Ohio: Chemical Research Co.; Barton, et al., 1997, Chemistry in Australia 64:4-6). 1,8-Cineole also has potential applications in alternative fuel production as it has been shown to prevent phase separation when used as an additive in ethanol-gasoline fuel blends (Barton and Tjandra, 1989, Fuel 68:11-17), and alternative fuels comprised of a gasoline/eucalyptus oil mixture (with 1,8-cineole as the major fuel component) resulted in an improved octane number and reduced carbon monoxide exhaust (U.S. Pat. No. 4,297,109).
Also, fenchocamphorone is a derivative of fenchol via a fenchene intermediate, both of which are monoterpenes (Croteau, et al., 1988, Journal of Biological Chemistry 263:15449-15453). Fenchone, also a monoterpene of similar derivations, is a volatile compound that is found as a major constituent of fennel seed oil (Azeez, S. (2008). Fennel. In Chemistry of Spices, pp. 227-241. Edited by Parthasarathy, V. A., Chempakam, B., & Zachariah, T. Cambridge, Mass.: CAB International). Fennel oil is also considered an essential plant oil and is valued for its strong flavor, but is also recognized as an antioxidant, hepatoprotective agent, anticancer agent, and other biological activities have been described for it (Azeez 2008; Cosimi et al., 2009, Journal of Stored Products Research 45:125-132).
Another example is 1,4-cyclohexadiene, which is a highly flammable cycloalkene that yields the natural monoterpene derivative, γ-terpinene, a component associated with many essential oils. 1,4-Cyclohexadiene also readily oxidizes to benzene by a number of different methods (Breton, et al., 2005, Electrochemistry Communications 7:1445-1448; Smith and Gray, 1990, Catalysis Letters 6:195-200; Hepworth et al., 2002, Aromatic Chemistry, pp. 129-134; Brooks, B. T. (1922). The Cyclic Non-benzoid Hydrocarbons: The Cyclohexane Series. In The Chemistry of Non-benzoid Hydrocarbons and Their Simple Derivatives, pp. 278-383. Edited by B. T. Brooks. New York, N.Y.: Chemical Catalog Company, Inc.) which gives it multiple applications in industrial chemistry. Benzene is a natural component of crude oil and gasoline and is a widely used chemical in the production of plastics, nylon, and resins, as well as some types of rubbers, detergents, lubricants, dyes, and pesticides (Agency for Toxic Substances and Disease Registry (ATSDR) (2007). Toxicological Profile for Benzene (Update). Atlanta, Ga.: U.S. Department of Public Health and Human Services, Public Health Service).
However, a major limiting factor in widespread industrial applications of these volatile compounds, particularly 1,8-cineole, pertains to its biological source. Currently, this monoterpenoid is produced solely by plants restricted to certain species of Eucalyptus, but also including Rosmarinus officinalis (Rosemary), and Thymus valgaris (Thyme) (Thomas, et al., 2000, Chemical Industry Digest (Special Millennium Issue) pp. 104-108), Melaleuca teretifolia (Southwell, et al., 2003, Journal of Essential Oil Research 15:339-341), and Mentha spicata (Cook, et al., 2007, The Journal of Essential Oil Research 19:225-230). A novel and more bountiful source for these compounds could significantly advance their industrial application profiles.
Endophytes, microorganisms that reside in the tissues of living plants (Stone et al., Microbial Endophytes, Ed. C. W. Bacon and J. F. White Marcel Decker, Inc, NY, 2000), are relatively unstudied and potential sources of novel natural products for exploitation in medicine, agriculture and industry. It is worthy to note, that of the nearly 300,000 plant species that exist on the earth, each individual plant is host to one or more endophytes. Only a handful of these plants have ever been completely studied relative to their endophytic biology. Consequently, the opportunity to find new and interesting endophytic microorganisms among myriads of plants in different settings, and ecosystems is great. Currently, endophytes are viewed as an outstanding source of bioactive natural products because there are so many of them occupying literally millions of unique biological niches (higher plants) growing in so many unusual environments.
It is well accepted that microorganisms can be a production source of chemical compounds, enzymes and other complexes that have industrial utility. The prospect that endophytes produce novel bioactive products stems from the idea that some endophytes may have coevolved with their respective higher plant, and as a result may produce certain phytochemicals characteristic of their hosts (Strobel and Daisy, 2003, Microbiology and Molecular Biology Reviews 67:491-502; Tan and Zou, 2001, Nat. Prod. Rep. 18:448-459). The enormous diversity generated by the presence of microbial life forms is amplified by their ability to inhabit novel niches, ranging from deep ocean sediments to the earth's thermal pools. Endophytic fungi inhabit one such biological niche and are characterized by their ability to asymptomatically colonize living plant tissues. There are untold numbers of potential novel fungal genera, of which endophytes constitute a significant proportion (Smith, et al., 2008, PloS 1 3(8):e3052). Ecosystems exhibiting the greatest plant diversity also seemingly exhibit the greatest abundance and diversity of microbial endophytes. Ultimately, biological diversity implies chemical diversity as constant chemical innovation is required in such highly competitive ecosystems. Thus, the search for novel endophytic microbes is ongoing, with activity of their natural products encompassing their use as antibiotics, antiviral compounds, anticancer agents, antioxidants, insecticides, antidiabetic agents, and immunosuppressive compounds (Strobel and Daisy, 2003, Microbiology and Molecular Biology Reviews 67:491-502).
One such endophyte is Hypoxylon spp., which is a fungal endophyte of Persea indica, an evergreen tree native to the Canary Islands, where it grows not in abundance but is found on several islands including Tenerife in the Laurisilva. Persea spp. are also native to Central and South America and were later introduced into Southern California (Zentmyer, et al., 1990, California Avocado Society 1990 Yearbook 74:239-242).
The complete analyses of fungal genomes in recent times indicate that many putative biosynthetic gene clusters are located in the distal regions of the chromosomes and exist in a heterochromatin state, with the constitutive genes often transcriptionally controlled by epigenetic regulation such as histone deacetylation and DNA methylation (Shwab et al., 2007, Eukaryot Cell 6:1656-1664). Several studies indicate that the inhibition of histone deacetylase activity, through gene disruption or use of epigenetic modulators, leads to the transcriptional activation of gene clusters, resulting in enhanced production of secondary metabolites (Shwab et al., 2007, Eukaryot Cell 6:1656-1664; Williams et al., 2008, Org Biomol Chem 6:1895-1897).
In fungi, both class I and class II histone deacetylases, and lysine- as well as arginine-specific methyltransferases have been identified (Brosch et al., 2008, FEMS Microbiol Rev 32:409-439). The modification of histones via acetylation and methylation reactions can have important effects on the production of fungal secondary metabolites (Shwab et al., 2007, Eukaryot Cell 6:1656-1664; Bok et al., 2009, Nat Chem Biol 5:462-464). These modifications can induce heritable epigenetic changes (Mooibroek et al., 1990, Mol Gen Genet. 222:41-48; Birch et al., 1998, J Appl Microbiol 85:417-424; Cheng et al., 2003, J Natl Cancer Inst 95:399-409). In addition, fungi treated with DNA methyltransferase and histone deacetylase inhibitors exhibited natural product profiles with enhanced chemical diversity, demonstrating that these small-molecule epigenetic modifiers are effective tools for rationally controlling the native expression of fungal biosynthetic pathways and generating biomolecules not previously known from the organism (Williams et al., 2008, Org Biomol Chem 6:1895-1897; Cichewicz, 2010, Nat Prod Rep 27:11-22). Undoubtedly, production of 1,8-cineole, among other volatile organic compounds such as 1-methyl-1,4-cyclohexadiene and (+)-α-methylene-α-fenchocamphorone by a fungal source, would have significant implications for use of such compounds in widespread industrial applications. Therefore, a need exists for the identification and production of volatile organic compounds produced by fungi. The present invention satisfies this need.